Smartglasses: no camera, controlled from a ring

yeah, I would consider putting the guts in a lanyard or in a pocket (connected by wire if bluetooth isn't fast/bandwidthy enough). But the projector may be too big by itself anyway. Magic Leap considered a kind of fibre-optic cable.

Another approach is to target usages where bulky headhear is already acceptable, e.g. helmets (cycling, go-pro-like extreme sports, construction hard-hats etc), googles (welders, scuba, WWI aircraft).

I think that kind of application is where smartglasses are presently maturing.

I like the ring concept though, like nintendo switch joy-cons, but even tinier.